Damper for an integrally bladed rotor

ABSTRACT

A Rotor includes a disk having a rim with an axial face, the rim defines a circumferential groove. A damper engaged with the rim at both the axial face and the circumferential groove.

BACKGROUND

The present disclosure relates to an integrally bladed rotor (IBR), andmore particularly to a damper system therefor.

Turbomachinery may include a rotor such as an integrally bladed rotor(IBR). The IBR eliminates individual blade attachments and shrouds buthas reduced inherent rotor damping. Reduced damping may result inelevated vibratory responses and potentially High Cycle Fatigue. Systemswhich involve friction dampers may be utilized to dissipate energy andaugment rotor damping.

BRIEF DESCRIPTION OF THE DRAWINGS

Various features will become apparent to those skilled in the art fromthe following detailed description of the disclosed non-limitingembodiment. The drawings that accompany the detailed description can bebriefly described as follows:

FIG. 1 is a general schematic view of an exemplary gas turbine enginefor use with the present disclosure;

FIG. 2 is a perspective, partial sectional view of a IBR;

FIG. 3 is a radial sectional view of the IBR illustrating a split ringdamper mounted thereto taken along line 3-3 in FIG. 2;

FIG. 4 is a facial sectional view of the IBR illustrating a split ringdamper mounted thereto taken along line 4-4 in FIG. 3;

FIG. 5 is a partial facial sectional view of the IBR illustrating asplit ring damper mounted thereto taken along line 5-5 in FIG. 3;

FIG. 6A is an idealization schematic representation of a force balancebetween the split ring damper and the IBR;

FIG. 6B is an idealization schematic representation of slip;

FIG. 7 is a perspective view of a portion of the split ring damperillustrating a non-limiting embodiment of a lightening feature;

FIG. 8 is a perspective view of a portion of the split ring damperillustrating another non-limiting embodiment of a lightening feature;and

FIG. 9 is another non-limiting embodiment of a split ring damper.

DETAILED DESCRIPTION

FIG. 1 schematically illustrates a gas turbine engine 20. The gasturbine engine 20 is disclosed herein as a two-spool turbofan thatgenerally incorporates a fan section 22, a compressor section 24, acombustor section 26 and a turbine section 28. Alternative engines mightinclude an augmentor section (not shown) among other systems orfeatures. The fan section 22 drives air along a bypass flowpath whilethe compressor section 24 drives air along a core flowpath forcompression and communication into the combustor section 26 thenexpansion through the turbine section 28. Although depicted as aturbofan gas turbine engine in the disclosed non-limiting embodiment, itshould be understood that the concepts described herein are not limitedto use with turbofans as the teachings may be applied to other types ofturbine engines.

The engine 20 generally includes a low speed spool 30 and a high speedspool 32 mounted for rotation about an engine central longitudinal axisC relative to an engine static structure 36 via several bearing systems38. It should be understood that various bearing systems 38 at variouslocations may alternatively or additionally be provided.

The low speed spool 30 generally includes an inner shaft 40 thatinterconnects a fan 42, a low pressure compressor 44 and a low pressureturbine 46. The inner shaft 40 is connected to the fan 42 through ageared architecture 48 to drive the fan 42 at a lower speed than the lowspeed spool 30. The high speed spool 32 includes an outer shaft 50 thatinterconnects a high pressure compressor 52 and high pressure turbine54. A combustor 56 is arranged between the high pressure compressor 52and the high pressure turbine 54. The inner shaft 40 and the outer shaft50 are concentric and rotate about the engine central longitudinal axisC which is collinear with their longitudinal axes.

The core airflow is compressed by the low pressure compressor 44 thenthe high pressure compressor 52, mixed and burned with fuel in thecombustor 56, then expanded over the high pressure turbine 54 and lowpressure turbine 46. The turbines 54, 46 rotationally drive therespective low speed spool 30 and high speed spool 32 in response to theexpansion.

With reference to FIG. 2, an integrally bladed rotor (IBR) 60 generallyincludes a rotor hub 62 from which a multiple of integrally machinedairfoils 66 extend for rotation about axis C. It should be understoodthat the IBR 60 may be utilized in the fan section 22, the compressorsection 24 and the turbine section 28 of the engine 20 as well as inother turbomachinery.

With reference to FIG. 3, an outer hub rim 64 and a hub inner surface 72are defined between a front face 68 and a rear face 70. The hub innersurface 72 is generally opposite the outer hub rim 64 and may be ofvarious contours. In one non-limiting embodiment, the hub inner surface72 may extend radially inward to define a web 74 and an inner bore 76.

The hub inner surface 72 defines a circumferential groove 78 whichreceives a split ring damper 80. The split ring damper 80 is generallyU-shaped in cross-section with a first leg 82 and a second leg 84interconnected by an interface 86. The split ring damper 80 may bemanufactured of a steel or titanium alloy with a coefficient of frictionin the range of 0.20 to 0.60. The split ring damper 80 may also becoated with a silver or other coating material to provide a desiredcoefficient of friction.

The first leg 82 is engaged with the groove 78 and the second leg 84 isadjacent to the face 68, 70 of the rotor hub 62. It should be understoodthat a split ring damper 80 may be mounted adjacent to either or bothfaces 68, 70. The second leg 84 may include a bulbed end 85 which ridesupon the face 68, 70. Dependant on, for example, the sensitivity of thevibration modes, the groove 78 may be of various widths to provide adesired rim stiffness.

The interface 86 between the first leg 82 and the second leg 84surrounds a radial lip 88 of the hub inner surface 72. A tab 90 on thesplit ring damper 80 engages a slot 92 on the radial lip 88 generallyopposite a split 94 in the split ring damper 80 (FIG. 4). At zerorotational speed, the split ring damper 80 has sufficient assemblypreload to maintain engagement with the rotor hub 62 up to, for example,20 Gs to prevent accidental disengagement.

The second leg 84 includes a multiple of radially extending slits 96(FIG. 5) which reduce the hoop stiffness for ease of assembly andconformity. In one disclosed non-limiting embodiment, the multiple ofradially extending slits 96 extend for approximately 50% of the radiallength of second leg 84.

An idealization of the force balance at the split ring damper 80 contactinterface is schematically illustrated in FIG. 6A. At operationalspeeds, the split ring damper 80 is in equilibrium. The appliedcentrifugal load F_(c) is reacted by contact forces F1, F2, and F3. Thecontact at three separate locations maximizes the benefits due to theexpected slip as the dissipated energy of the system is additive fromall sources for a given mode of vibration. The split ring damper 80minimizes the impact on rim stiffness and provides multiple points ofcontact which capture both axial and radial deflections to provide arespectively higher system damping.

It should be noted that an optimum configuration is stiff in thecircumferential direction yet light weight to ensure slip will takeplace. This is expressed in the well known relationship:

KΔ

μN

where

K=damper stiffness in the tangential direction,

Δ=deflection of damper,

μ=coefficient of friction between damper and IBR.

N=the contact force normal to the direction of damper motion.

For a single point of contact, for example, point 1, the condition forslip is K₁Δ₁

μF₁ as shown in FIG. 6B.

The amount of energy dissipated during one cycle of oscillation is theshaded area A₁. For multiple points of contact undergoing large enoughvibration amplitudes, slip will occur at each location contributing tothe overall system damping A*, where

$A^{*} = {\sum\limits_{i = 1}^{3}A_{i}}$

With reference to FIG. 7, the first leg 82 may include scallops 98 toreduce weight yet maintain relatively high stiffness. Alternatively,lightening apertures 10 may be formed through the first leg 82 (FIG. 8).

With reference to FIG. 9, another non-limiting embodiment of the splitring damper 80′ includes a damper ring 102 mounted within a groove 104formed in the face 68′, 70′ of the rotor hub 62′. The damper ring 102 iscontained within the groove 104 with a cover 106 welded or otherwiseattached to the face 68′, 70′.

The split ring damper 80 is effective for both axial and radial modes,does not result in a significant change of rim stiffness such that theairfoil fundamental mode frequencies are not changed by more than 1 to2%; provides multiple points of contact which capture both axial andradial deflections resulting in higher system damping; and does notclock circumferentially relative to the disk to assure the maintenanceof rotor balance.

It should be understood that relative positional terms such as“forward,” “aft,” “upper,” “lower,” “above,” “below,” and the like arewith reference to the normal operational attitude of the vehicle andshould not be considered otherwise limiting.

It should be understood that like reference numerals identifycorresponding or similar elements throughout the several drawings. Itshould also be understood that although a particular componentarrangement is disclosed in the illustrated embodiment, otherarrangements will benefit herefrom.

Although particular step sequences are shown, described, and claimed, itshould be understood that steps may be performed in any order, separatedor combined unless otherwise indicated and will still benefit from thepresent disclosure.

The foregoing description is exemplary rather than defined by thelimitations within. Various non-limiting embodiments are disclosedherein, however, one of ordinary skill in the art would recognize thatvarious modifications and variations in light of the above teachingswill fall within the scope of the appended claims. It is therefore to beunderstood that within the scope of the appended claims, the disclosuremay be practiced other than as specifically described. For that reasonthe appended claims should be studied to determine true scope andcontent.

1. A rotor comprising: a disk having a rim, said rim having an axialface facing one of a forward or rearward direction, said rim defines acircumferential groove; and a damper engaged with said rim at both saidaxial face and said circumferential groove.
 2. The rotor as recited inclaim 1, wherein said axial face is a front face.
 3. The rotor asrecited in claim 1, wherein said axial face is a rear face.
 4. The rotoras recited in claim 1, wherein said damper is a split ring damper thatis U-shaped in cross section.
 5. An integrally bladed rotor comprising:a rotor hub that defines a hub face facing one of a forward or rearwarddirection and a hub inner surface with a circumferential groove withinsaid hub inner surface; and a split ring damper mounted within saidcircumferential groove and in contact with said hub face.
 6. Theintegrally bladed rotor as recited in claim 5, wherein said split ringincludes a first leg and a second leg, said first leg engaged withinsaid circumferential groove and said second leg in contact with said hubface.
 7. The integrally bladed rotor as recited in claim 6, wherein saidfirst leg includes a multiple of scallops.
 8. The integrally bladedrotor as recited in claim 6, wherein said first leg includes a multipleof lightening apertures.
 9. The integrally bladed rotor as recited inclaim 6, wherein said second leg includes a multiple of radial slits.10. The integrally bladed rotor as recited in claim 6, furthercomprising a hub rim opposite said hub inner surface, a multiple ofairfoils integral with said hub rim.
 11. The integrally bladed rotor asrecited in claim 6, wherein said split ring damper defines a coefficientof friction in the range of 0.20 to 0.60. 12-16. (canceled)
 17. Anintegrally bladed rotor comprising: a rotor hub that defines a hub facefacing one of a forward or rearward direction and a hub rim transverseto said hub face; a multiple of airfoils integral with said hub rim; anda split ring damper mounted to said rotor hub and including a portion incontact with said hub face.
 18. The integrally bladed rotor as recitedin claim 17, wherein said split ring damper is mounted within acircumferential groove within a hub inner surface generally oppositesaid hub rim.
 19. The integrally bladed rotor as recited in claim 18,wherein said split ring includes a first leg and a second leg, saidfirst leg engaged within said circumferential groove and said second legin contact with said hub face.
 20. (canceled)
 21. The integrally bladedrotor as recited in claim 17, wherein said rotor hub comprises a hubinner surface facing a longitudinal axis about which said rotor hubrotates and said hub rim being spaced radially outwardly relative tosaid hub inner surface, and wherein said hub face extends radiallyinwardly from said hub rim to said hub inner surface.
 22. The integrallybladed rotor as recited in claim 21, wherein said hub face comprises afront face of said rotor hub and faces the forward direction.
 23. Theintegrally bladed rotor as recited in claim 21, wherein said hub facecomprises a rear face of said rotor hub and faces the rearwarddirection.
 24. The integrally bladed rotor as recited in claim 21,including a circumferential groove formed within said hub inner surface,and wherein said split ring damper includes a first leg mounted withinsaid circumferential groove and a second leg that extends from saidfirst leg to surround a radial lip of said hub inner surface and tocontact said hub face.
 25. The rotor as recited in claim 1, wherein saiddisk includes a rotor hub having a hub inner surface facing alongitudinal axis about which said rotor hub rotates and said rim beingspaced radially outwardly relative to said hub inner surface, andwherein said axial face extends radially inwardly from said rim to saidhub inner surface.
 26. The rotor as recited in claim 25, wherein saidcircumferential groove is formed within said hub inner surface, andwherein said damper comprises a split ring damper with a first legmounted within said circumferential groove and a second leg that extendsfrom said first leg, surrounds a radial lip of said hub inner surface,and extends radially outwardly to contact said axial face.
 27. Theintegrally bladed rotor as recited in claim 5, wherein said hub innersurface faces a longitudinal center axis about which said rotor hubrotates and wherein rotor hub includes an outer hub rim that is spacedradially outwardly relative to said hub inner surface, said outer hubrim supporting a plurality of airfoils, and wherein said hub faceextends radially inwardly from said outer hub rim to said hub innersurface.
 28. The integrally bladed rotor as recited in claim 27, whereinsaid circumferential groove is formed within said hub inner surface, andwherein said split ring damper includes a first leg mounted within saidcircumferential groove and a second leg that extends from said firstleg, surrounds a radial lip of said hub inner surface, and extendsradially outwardly to contact said hub face.
 29. The integrally bladedrotor as recited in claim 27 wherein said hub face comprises a frontface facing the forward direction.
 30. The integrally bladed rotor asrecited in claim 27 wherein said hub face comprises a rear face facingthe rearward direction.